Discovery of a Pleistocene mysticete whale, Georgia Bight (USA)

Abstract

Subfossil evidence, including a nearly complete dentary (~77%) (left mandible) and two badly eroded vertebrae, of a mysticete whale, were recovered, underwater, from an in situ context, in the Georgia Bight, 30 km offshore St. Catherine's Island, Georgia. The discovery of the mandible was initially made in 2006 but excavation was not completed until the summer of 2008. Two badly preserved vertebrae were found lying nearby having eroded from the same outcrop as the dentary. The two vertebrae were dated but not analyzed in this report. Direct dating of the subfossils, with the Accelerator Mass Spectometry radiocarbon technique (AMS), using bioapatite, rather than collagen, suggests a common age range for the skeletal materials, 34,000 to 37,000 ka, but it's speculative to assign these remains to the same animal or, for that matter, the same taxon. The ages determined for the subfossils are in good agreement with the age of the geological deposit, a shell coquina, as previously determined by AMS dating of inclusions and by direct dating of the sediments using Optical Stimulated Luminescence (OSL) dating. Additionally, amino acid raceminization (AAR) ages were obtained for the coquina. Our comparative analysis supports a diagnosis of a dentary of a mysticete whale. Further comparison of preserved morphological characters with those for mysticete mandibles, support a further diagnosis as balaenopterid or eschrichtiid. Coupled with recent, Pleistocene aged discoveries, in Europe, in the North Sea basin, these remains could provide well-dated, new, North American evidence for the extirpated gray whale in the Atlantic basin of the Quaternary.

An Early Pleistocene gray whale (Cetacea: Eschrichtiidae) from the Rio Dell Formation of northern California

“…2.3, 2.6). Repenning (1983), Barnes and McLeod (1984), Mead and Mitchell (1984), Post (2005), Ichishima et al (2006), Garrison et al (2012), Noakes et al (2013), Tsai et al (2014), and this study. Subfossil records from Jones and Swartz (2009, fig.…”

Recent dating of extinct Atlantic gray whale fossils, (Eschrichtius robustus), Georgia Bight and Florida, western Atlantic Ocean

“…These ages are clearly bimodal in their distribution suggesting either that: (1) any population surviving post-LGM is geologically "invisible", due to a lack of fossil evidence; or (2) the lack of finds reflects their true absence, indicating a significant decline or even the effective extirpation of gray whales across the north Atlantic Ocean in the period between ~40 ka and ~11 ka. The argument in favor for the latter may be further supported by geologic evidence for a much-reduced habitat in the north Atlantic during LGM due to the subaerial exposure of both the North Sea/Baltic and the Georgia Bight and Florida continental shelves (Alter et al 2015;Garrison et al 2008;2012;Harris et al 2013). Fossil evidence for the gray whale, however, may yet be found for the post-40 ka -11 ka interval on areas of the Atlantic continental shelf that were inundated at or during the last low stand.…”

Peer Review #1 of "Recent dating of extinct Atlantic gray whale fossils, (Eschrichtius robustus), Georgia Bight and Florida, western Atlantic Ocean (v0.2)"

“…These ages are clearly bimodal in their distribution suggesting either that: (1) any population surviving post-LGM is geologically "invisible", due to a lack of fossil evidence; or (2) the lack of finds reflects their true absence, indicating a significant decline or even the effective extirpation of gray whales across the north Atlantic Ocean in the period between ~40 ka and ~11 ka. The argument in favor for the latter may be further supported by geologic evidence for a much-reduced habitat in the north Atlantic during LGM due to the subaerial exposure of both the North Sea/Baltic and the Georgia Bight and Florida continental shelves (Alter et al 2015;Garrison et al 2008;2012;Harris et al 2013). Fossil evidence for the gray whale, however, may yet be found for the post-40 ka -11 ka interval on areas of the Atlantic continental shelf that were inundated at or during the last low stand.…”

“…Manuscript to be reviewed and the dentary based on its previous diagnosis (Garrison, et al, 2012) as this unique mysticete whale but both secure morphological and genomic attributes are lacking for the remainder of our samplethree dentary fragments. To include these latter specimens in our assessment of an extirpated population is problematic.…”

“…1). At J-Reef the shell beds are in a conformable relationship with finer grained sediment that dates to no earlier than the late Pleistocene (Garrison, et al, 2012). The four dentary (?)…”